If you're using the preset mixers, you won't be able to use more than one of them to affect a single function. If you're using flaperon mixer, then the elevator -> flap mixer won't automatically link to the aileron channel. It will only affect the flap channel.

If you want flaperons and elevator -> flap mixing, you'll have to use the pmix's.

For flaperons, you'll need 2 pmix's: aileron->flap, and flap->aileron. Link ON, Trim ON.

To get the elevators to activate the flaperons like a control line model, you'll need to use another 2 mixes: elevator->aileron, elevator-> flap. Link ON, Trim ON.